It is well-known to use MOINEAU type pumps driven into rotation by rods which are themselves driven into rotation from a surface installation. However, the rotary speed of the pump rotor is limited notably by the mechanical strength of the rods, the dynamic frictions inside the well, or the mechanical mounting of the rotor in the pump stator. In fact, concerning the latter limitation, the nature of the effluents in which the pump is set, the pressure and the temperature prevailing at the bottom of a well complicate considerably the use of more efficient means for mounting the rotor in the stator. It is well-known that such mounting means require at least lubrication of the mechanical parts in motion. Under the conditions described above, tight and temperature-resisting mountings would thus be necessary to protect the fluid lubricating the mechanical means against pollution due to the effluent produced.
The present invention provides a solution to this technical problem by allowing the effluent itself to be used as a lubricating fluid, by circulating it through the mechanical mounting means driving the rotor.
Furthermore, according to a variant of the present invention, it is also possible to add to these mounting means a speed step-up gear for increasing the rotary speed of the rotor with respect to the rotary speed of the rods. A higher pumping capacity may thus be obtained with a reasonable rotary speed of the rods. It should be reminded that the capacity of a rotary positive-displacement pump is substantially proportional to the rotary speed of the rotor.